This invention relates to a storage vessel for liquid substances which are supplied to an end-user device, having a device for cleaning the connecting pieces and lines when the storage vessel is changed.
A storage vessel is used to supply liquid substances to a reactor for chemical vapor deposition (CVD). Such CVD reactors are used to produce chips, i.e. integrated microcircuits, and similar elements. In addition, e.g. devices for producing hard-material layers or glass fibers must be provided with liquid chemicals. To meet the constantly rising demands of such equipment, one must use extremely high-purity substances for the corresponding processes.
When the storage vessel containing the substance which is supplied to the device is replaced, however, there is a danger of impurities arising in the lines from the storage vessel to the reactors, in particular through inevitable air admission when the storage vessel is changed, which can lead to decomposition of residues of the liquid substance in the supply line, especially since the substances, usually organic metal or semimetal compounds, are often extremely sensitive to air and/or moisture.
In order to eliminate the impurities one has previously cleaned the line connecting the rising line with the device and the pressure gas line for pressurizing the substance in the storage vessel by evacuating the particular line with a vacuum pump and then drawing in a solvent from a solvent vessel after changing the storage vessel, the solvent then being emptied into a waste vessel. This flushing process is generally performed several times. This cleaning procedure requires carefully working, reliable operators, is time-consuming (e.g. one must monitor the levels of the solvent vessel and waste vessel for spent solvent and the vacuum), and rather elaborate because of the additional solvent vessel and waste vessel for spent solvent.
The object of the invention is therefore to provide an easily handled, reliable device for cleaning the connecting pieces and lines of a storage vessel, such as the type described above.
This is obtained according to the invention with a storage vessel for liquid high-purity substances having an integrated device for cleaning the connecting pieces and lines of the storage vessel. Advantageous embodiments of the inventive storage vessel are disclosed.
That is, according to the invention the storage vessel is formed as a package together with the solvent vessel and/or an evacuated vessel serving as a vacuum source for the flushing process.
Further, one can provide a waste vessel for the spent solvent used for flushing. This vessel can also be combined with the evacuated vessel. The storage vessel can thus form a package with one, two or three further vessels, being replaced as a whole by a new package when the storage vessel is changed.
This considerably simplifies logistics while at the same time considerably reducing the possibility of operating errors. For example the solvent vessel, the vessel for receiving spent solvent and the evacuated vessel can be designed in such a way that sufficient solvent, capacity for used solvent and vacuum are always available for flushing when the storage vessel is changed.
In the simplest case, the package may comprise only one vessel for solvent in addition to the storage vessel for the liquid substance. The vacuum for cleaning the connecting pieces can then be produced by a vacuum pump for example, and for receiving spent solvent one may provide a waste vessel independent of the package.
It is also possible to provide a package with only an evacuated vessel as a vacuum source for flushing the connecting pieces together with the storage vessel, or a package only with the waste vessel for used solvent in addition to the storage vessel.
However, along with the storage vessel, the package preferably comprises both a solvent vessel and an evacuated vessel as a vacuum source which may at the same time form the vessel for receiving used solvent.
The vessel for solvent, the evacuated vessel and a separate waste vessel for spent solvent, if present with the evacuated vessel, can be combined into a package with the storage vessel in a great variety of ways. For example, the vessels can be disposed beside, below or within the storage vessel for the liquid substance. Several vessels for solvent, the vacuum and/or for used solvent can be provided. The vessels can be formed by double or multiple jackets around the main vessel. However, they always form a package together with the storage vessel which can be used for transport and for stockpiling.
The evacuated vessel can contain a solid absorbent, for example a molecular sieve, e.g. a zeolite. The absorbent is provided for maintaining the vacuum in the evacuated vessel, i.e. to adsorb air penetrating the evacuated vessel through leaks. When the evacuated vessel receives spent solvent, the absorbent serves to absorb the solvent. The properties of the absorbent are thus adapted to the solvent. That is, with hydrophobic solvents, such as hexane, one uses a hydrophobic absorbent and with hydrophilic solvents, for example ethanol, one uses a hydrophilic adsorbent.
The solvent vessel, the evacuated vessel and, if present, the vessel for spent solvent are adapted to be connected via a shut-off device to the connecting piece of the pressure gas line and the rising line, preferably between the coupling and the shut-off device of the pressure gas line or between the coupling and the shut-off device of the rising line. The shut-off devices may be valves, cocks or the like. Preferably, the connecting piece of the pressure gas line to the storage vessel is connected with the connecting piece of the rising line by a connecting line with a shut-off device.
The shut-off devices in the connecting pieces of the pressure gas line and the rising line and the shut-off devices connecting the solvent vessel, the evacuated vessel and, if present, the vessel for spent solvent to the connecting pieces of the pressure gas line and the rising line are preferably connected to a plate provided with channels having connected thereto, besides the rising line, the connecting pieces for the pressure gas line and the rising line as well as optionally a port for supplying pressure gas to the storage vessel. A further channel in the plate can be formed by the connecting line interconnecting the connecting pieces for the pressure gas line and the rising line.
Such a plate with attached shut-off valves, which are also designated xe2x80x9csurface mounted devices,xe2x80x9d is characterized by short channels and thus small dead volumes, a better seal and simple mounting because e.g. the shut-off devices need only be screwed into corresponding tapholes with a seal in the plate. The connecting pieces and optionally the couplings for the pressure gas line and the rising line can likewise be integrated in the plate.
The shut-off devices in the connecting pieces of the pressure gas line and the rising line as well as the shut-off devices connecting the solvent vessel, the evacuated vessel and/or the vessel for spent solvent to the connecting pieces of the pressure gas line and the rising line are preferably formed so as to be automatically operable. For automatic operation, the shut-off devices can be formed so as to be operable pneumatically or electrically.
Preferably, a control unit is provided for driving the shut-off devices in such away that the cleaning process takes place automatically after the package with the storage vessel is changed.
If the shut-off devices are driven by an external control unit via electric control lines, it is advantageous to connect the control line from the shut-off devices with a plug, socket or similar plug-type part to be fitted with a mating part for connection with the control unit. This prevents errors from occurring when the control line is connected with the control unit after a change of package. The plug-type part can at the same time connect the level measuring device in the storage vessel with the level indicator.